Apparatus for the production of green test specimens from artificial carbon

ABSTRACT

Apparatus for the production of test specimens from green artificial carbon by shaking of a warm granular mass in a stationary mold, the bottom of which is formed by a closure plate vertically movable in the lower part of the mold, which rests on spring elements and can be set in vibration in the vertical direction by means of two oppositely rotating motors and is closable at the top by a counter-plate. The apparatus is distinguished in that said counter-plate is pressable by means of an upper cylinder by oil pressure against the carbon mass by virtue of the installation of a non-return valve and a fine needle valve connected parallel therewith in the oil conduit in such a way that it can follow the variation of height of the compacting mass.

United States Patent 1191 Fischer 1 Oct. 9, 1973 [5 APPARATUS FOR THE PRODUCTION OF 2,831,230 4/1958 Neth et a1. 425 421 GREEN TEST SPECIMENS FROM 3,443,626 5/1969 Miller 164/303 X ARTIFICIAL CARBON 3,712,785 1/1973 l-lirt et a1. 425/425 x Inventor: Werner Karl Fischer, Venthone,

Switzerland Assignee: Swiss Aluminium Ltd., Chippis,

Switzerland Filed: Apr. 25, 1972 Appl. No.: 247,359

Foreign Application Priority Data Apr. 28, 1971 Switzerland 6197/71 References Cited UNITED STATES PATENTS 7/1925 Harrison 425/421 X Primary Examiner-R. Spencer Annear Attorney-Ernest F. Marmorek [5 7] ABSTRACT Apparatus for the production of test specimens from green artificial carbon by shaking of a warm granular mass in a stationary mold, the bottom of which is formed by a closure plate vertically movable in the lower part of the mold, which rests on spring elements and can be set in vibration in the vertical direction by means of two oppositely rotating motors and is closable at the top by a counter-plate. The apparatus is distinguished in that said counter-plate is pressable by means of an upper cylinder by oil pressure against the carbon mass by virtue of the installation of a nonreturn valve and a fine needle valve connected parallel therewith in the oil conduit in such a way that it can follow the variation of height of the compacting mass.

1 Claim, 1 Drawing Figure APPARATUS FOR THE PRODUCTION OF GREEN TEST SPECIMENS FROM ARTIFICIAL CARBON The present invention relates to an apparatus for the production of green (unfired, unbaked) test specimens from artificial carbon.

Very large artificial carbon bodies are frequently needed in industry. These are usually produced by firing (baking) of a granular mass of carbon-containing dry material with addition of cokable binding agent. According to the nature of the dry material (chemical and physical composition) and according to the binding agent, if one is used, also according to the manner of processing (for example by pressing or by vibration), according to pressure and the course of the firing temperature, artificial carbon bodies are obtained which have properties differing from one another.

In the manufacture of artificial carbon it is extremely important to know in advance what properties the artificial carbon bodies will receive. Having regard to the size of the artificial carbon bodies and/or to the quantity of artificial carbon bodies to be produced at the same time, it is obvious to test out the various parameters on test specimens, before instructions are given for large scale manufacture.

The following methods of testing new pairs of materials and different parameters for the production of green test specimens from artificial carbon, that is of artificial carbon test specimens before firing, are principally known:

a. Testing in the production plant, involving great expenditure of material and causing great losses of material if the experiment has an unfavourable course;

b. The production of test specimens in chill moulds by means of accessory compacting devices, such as pneumatic hammers, bench presses and the like, in which case mostly inhomogeneous specimens are produced which are not representative for the subsequent large scale manufacture;

c. The production of test specimens on small presses which imitate the production plant, that is to say work with high pressures and floating chill moulds. As a result of the expensive construction and controlling these small presses are very expensive. Nevertheless the green test specimens produced on them permit good indications of the large scale production of pressed artificial carbon bodies, for example electrodes for the manufacture of aluminum.

On account of the ever larger electrode formats, green artificial carbons are produced more and more by shaking or vibration compacting. The results with the test specimens produced on small presses do not however permit reliable conclusions as to the behaviour of shaken artificial carbon bodies. Therefore it is important inthe case of this more recent artificial carbon manufacturing method to produce the green test specimens by shaking too.

The invention was based upon the desire to produce green artificial carbon test specimens in any desired manner which can be constantly repeated and in considerable numbers. However the problem was not easy to solve. Since small artificial carbon masses of about 8 to 10 kg. react less inertly to vibrations than do those of production sizes, for example 500 to 800 kg., it is difficult to obtain test specimens with the same apparent density and the same physical properties as those of the artificial carbon bodies in production sizes.

Now the invention relates to an apparatus and a process for the production of test specimens from green artificial carbon by shaking of a warm, granular mass in a stationary mold which is rigidly connected with the machine frame and the bottom of which, which is formed by a closure plate vertically movable in the lower part of the mold and rests on spring elements, can be set in vibration in the vertical direction with the aid of two oppositely rotating eccentric motors, and which is closable at the top by a counter-plate. The apparatus is distinguished in that the counter-plate is pressable by means of an upper cylinder by oil pressure against the artificial carbon mass with which the mold is charged in operation, by virtue of the installation of a non-return valve and a fine needle valve connected in parallel therewith in the oil conduit, in such a way that it can follow the variation of height of the compacting artificial carbon mass.

The process according to the invention in which the apparatus according to the invention is used is characterised in that the counter-plate is pressed against the artificial carbon mass in such a way that it can follow the variation of height of the compacting mass, without thereby exceeding the pressure transmitted by the closure plate at maximum centrifugal force of the eccentric motors. Preferably precaution is taken so that when compacting has progressed the counter-plate accompanies the vibration with an amplitude lying between one-half and three quarters of the amplitude of the vibrations of the closure plate.

At the beginning of pressing, oil flows through the non-return valve at every vibration stroke. The counter-plate moves by jerks exclusively downwards. The mass is still very compressible. Practically no oil yet flows through the parallel-connected fine needle valve. As soon as the mass is in the vicinity of final compacting, the counter pressure upon the counter-plate increases and oil begins to flow back through the fine needle valve, namely at every stroke of the bottom. An equilibrium can be established.

In the operation of the apparatus according to the invention three extreme cases can be conceived:

l. The fine needle valve is kept closed. At every downward movement of the closure plate of the mold oil follows up through the non-return valve into the upper cylinder. In the following upward movement of the closure plate in in the upper cylinder. The spring elements upon which the closure plate rests are finally crushed, whereby vibration of the bottom is prevented.

2. The fine needle valve is entirely opened. At every positive amplitude deflection the counter-plate can be forced upwards and thus finally loses contact with the artificial carbon mass.

3. The loss of contact with the mass when the fine needle valve is open can be prevented by increasing the pressure in the hydraulic system. In this way the contact with the mass is maintained, but the spring elements are too greatly compressed, so that the vibrations of the bottom are greatly attenuated or even prevented.

The apparatus according to the invention renders possible the establishment of a state of equilibrium between the return fiow quantity of oil through the fine needle valve and the pressure setting in the hydraulic system.

The FIGURE illustrates diagrammatically an advantageous form of embodiment of the apparatus according to the invention.

designates a machine frame which is firmly connected with a concrete foundation 12 resisting on spring elements 11. A mold 13 of a round steel tube with an internal diameter of 200 mm., a wall thickness of 16 mm. and a height of 300 mm. is welded in a steel plate 14 which in turn is welded with the machine frame 10. The closure plate 15, which serves as bottom for the mold 135, is screwed to the piston rod 16 which carries the piston 17 and is movable in the ejector cylinder 18. In the position as illustrated the closure plate 7 is seated on the collar 19 which is welded on to the base plate 20. The base plate 20 carries the eccentric motors 21 and 22, rotating oppositely in operation, and bears by means of four spring elements 23 each of four helical springs 24 on the machine frame 10. The ejector cylinder 18 is screwed to the base plate 20. 25 is a round counter-plate which is screwed to the piston rod 27 of the oil pressure cylinder 28 which actuates the piston 26. 29 and 30 designate oil conduits which lead to the upper oil pressure cylinder 28. The oil conduit 29 is provided with a non-return valve 31 and with a fine needle valve 32 connected in parallel therewith. The non-return valve 31 is so arranged that the oil which is under pressure during the vibration or compacting and is delivered by the pump assembly 33 can flow only in the direction towards the oil pressure cylinder 28. In order however also to render possible an upward movement of the piston 26, for example for the -purpose of charging of the mold 13 with granular artificial carbon mass, the non-return valve 31 can be hydraulically released by means of the control conduit 34. Such hydraulically releasable non-return valves are usual in commerce. As fine needle valve there may be considered for example the colorflow fine needle valve (2) which is described and illustrated on page 1 of Catalogue 3160 of January, 1970 of the Manatrol Division of the Firm Parker-Hannifin. Such a fine needle valve permits oil to flow through in both directions and is of course regulable.

The pump assembly 33 essentially comprises an oil reservoir, a pump driven by an electric motor and a pressure-limiting valve which is adjustable during operation, and is arranged in a control desk 35. Such pump assemblies can be obtained on the market, so that further description is superfluous. Reference is made for example to the pump units type GR of the Firm Oelhydraulik Hagenbuch AG, 6030 Ebikon, Switzerland.

At the beginning of an operation the counter-plate 25 is lifted by means of the oil pressure cylinder 28. For

the lifting of the counter-plate 25 the oil conduit 30 is placed under pressure from the pump assembly 33, the non-return valve 31 being released, and oil is fed to the cylinder chamber beneath the piston 26. The closure plate 15 closes off the mold 13 in the downward direction and is drawn by the piston 17 of the ejector cylinder 18 firmly against the collar 19. When the counterplate 25 is lifted the mold 13 is charged with granular artificial carbon mass 36. Then the pressure in the oil conduit 30 is released, whereby the non-return valve 31 is set in action again, and at the same time the: oil conduit 29 is set under pressure, which firstly effects a downward movement of the piston 26 and thus introduction of the counter-plate 25 into the mold 13. The counter-plate 25 comes into contact with the charge of granular artificial carbon mass 36 and presses upon the mass. Thus the closure plate 15 in common with the base plate 20 is pressed downwards against the spring elements 23, which yield somewhat. A state of equilibrium necessarily establishes itself between the force applied by the oil pressure cylinder 28 and the reaction of the spring elements 23. It must be taken into consideration here that even at the maximum expected amplitude of the vibrations which are forced upon the system by the eccentric motors, the spring elements 23 must not be overstressed, for example not entirely compressed. After the state of equilibrium is reached the eccentric motors are set in operation, and the base plate 20 together with the closure plate 15 begin to vibrate. By selection of the oil pressure in the oil conduit 29 the counter plate 25 is pressed against the charge 36 in such a way that it can follow the variation of height of the compacting artificial carbon mass 36 without thereby exceeding the counter pressure transmitted by the closure plate 15 to the mass 36 at maximum centrifugal force of the eccentric motors, and when the compacting has progressed the counter-plate 25 accompanies vibration with an amplitude lying between 5% and "$3 of the amplitude of the vibrations of the closure plate.

After the final degree of compacting of the artificial carbon mass 36 is reached, for example after 2 to 3 minutes, the eccentric motors are switched off, the pressure in the oil conduit 29 is eliminated and the oil conduit 30 is placed under pressure, the non-return valve 31 being released. The counter-plate 25 is lifted by the pressure in the oil conduit 30. Then the oil pressure ejector cylinder 18 lifts the compacted artificial carbon specimen, weighing about 8 kg., to the level of the upper mold edge whence it can be removed. Finally the closure plate 15 is drawn again against the collar 19 and a new operation can commence.

ln the following table the physical and chemical test data of test specimens which were produced in an apparatus according to the invention will be compared with data from current production:

For the determination of the reactivity the test specimen is subjected after baking (firing) to a constant CO current at 950 for 7 hours. A part of the carbon of the test specimen is oxidised by the CO into CO and the residue is the residual specimen.

As may be seen the data obtained conform well with one another, so that by means of the apparatus according to the invention test specimens are obtained which give actual information as to artificial carbon bodies which are obtained in the production plant, taking account of the same parameters as in the apparatus according to the invention.

1 claim:

1. Apparatus for the production of test specimens from green artificial carbon by shaking of a warm,

by means of an upper cylinder (28) by oil pressure against the artificial carbon mass (36) with which the mold (13) is charged in operation, by virtue of the installation of a non-return valve (31) and a fine needle valve (32) connected parallel therewith in the oil conduit (29), in such a way that it can follow the variation of height of the compacting mass. 

1. Apparatus for the production of test specimens from green artificial carbon by shaking of a warm, granular mass in a stationary mold, which is rigidly connected with the machine frame, the bottom of which is formed by a closure plate vertically movable in the lower part of the chill mold, which rests on spring elements and can be set in vibration in the vertical direction with the aid of two oppositely rotating eccentric motors and is closable at the top by a counter-plate, characterised in that the counter-plate (25) is pressable by means of an upper cylinder (28) by oil pressure against the artificial carbon mass (36) with which the mold (13) is charged in operation, by virtue of the installation of a non-return valve (31) and a fine needle valve (32) connected parallel therewith in the oil conduit (29), in such a way that it can follow the variation of height of the compacting mass. 